Electrical devices which are formed as generators as a rule comprise a rotor, a stator, and also a casing which encloses the stator. Stator winding bars, which are constructed from strands which are insulated against each other and arranged one above the other in slots, in this case are arranged in a stator body, especially in a laminated stator core, on the end faces of which they project into an end-winding space. There, they are bent in the radial direction and in the circumferential direction, and at their ends are electrically and mechanically connected to a winding. The end-winding space in this case accommodates the stator end windings and also the connectors and output conductors. In the case of electrical devices with indirectly cooled stator winding, a gaseous cooling medium, as a rule cooling air, is introduced into the rotor in the region of the rotor hub. By slots in the rotor rim it discharges in an air gap in order to impinge upon essentially radially extending passages of the stator for the purpose of cooling the stator winding. A partial flow of the cooling gas flow is axially deflected in the direction of the end-winding space and used for cooling the components which are located there, especially the connectors and the output conductors. Alternatively, this partial flow can also be provided by a ventilation device which is installed on the rotor on the end face, especially by a fan or by an external fan which is arranged in the region of the end windings. Especially in the case of modern high-power units, reliable cooling of the connectors and output conductors represents an increasing challenge in this case. While the part of the winding which is embedded in the winding slots is cooled in a concentrated manner, the exposed winding parts in the end-winding space, especially the connectors and output conductors, are exposed to the risk of excessive heating. On account of their position, like in the lee of the end windings, a defined cooling of the connectors and output conductors is simply difficult to realize. The flow velocity of the cooling gas flow in this region, moreover, is low and the cooling gas flow is unevenly distributed so that the flow parameters are altogether simply difficult to control.
Pressure losses and flow deflections during exposure of the end windings to throughflow, furthermore, bring about an uneven impingement upon the downstream components which are to be cooled, and the comparatively low flow velocity with the inevitable consequence of the risk of an at least locally unsatisfactory cooling of these components. A theoretically possible increasing of the volumetric flow of the cooling gas flow in this region does not provide a significant alleviation of this problem.
In the case of electrical devices with directly cooled stator winding, however, the described problems do not occur since the cooling gas which flows through the hollow conductor brings about an adequate cooling of the conductor bars. Measures for such a direct cooling of the conductor bars, however, are associated with significant cost.